1. Field of the Invention
Aspects of the present invention generally relate to an inkjet liquid discharge head for discharging liquid such as ink to perform recording on a recording medium.
2. Description of the Related Art
Among inkjet recording methods, a method for discharging ink droplets having different sizes to express gradations has been known. Particularly, recording dots including relatively small ink droplets are provided from a light portion to a halftone portion of an image, whereas recording dots including relatively large ink droplets are provided from the halftone portion to a dark portion of the image. A cross-sectional area and a flow path resistance of an ink supply path and a flow path are adjusted according to sizes of the liquid droplets so that different sizes of the ink droplets are formed.
Since a discharge port positioned in a leading edge of a flow path is exposed to the air, moisture is evaporated from the discharge port while discharge is not being performed. Consequently, if supply of moisture from the flow path is too late, the density of solvent and dye included in ink increases or viscosity of the ink increases at the leading edge of the flow path. Such an increase in density or viscosity causes an increase in print density. Moreover, when ink is not discharged for a certain time period, there are cases where a liquid droplet supposed to be discharged first is not discharged from a discharge port, or a liquid droplet discharged first from a discharge port is obliquely discharged.
Japanese Patent Application Laid-Open No. 2005-28741 discusses a discharge port (hereinafter referred to as a large discharge port) for discharging large liquid droplets and a discharge port (hereinafter referred to as a small discharge port) for discharging small liquid droplets are arranged serially adjacent to each other in one flow path such that the small discharge port is positioned on an upstream side relative to an ink supply direction. When large liquid droplets are discharged from the large discharge port, and then the large discharge port is refilled, the ink near the small discharge port is refreshed by flow of ink.
In a liquid discharge head, printing discharge and preliminary discharge are known as two ink discharge modes. The printing discharge is discharge of ink to print the ink on a print medium. The preliminary discharge is discharge of ink to refresh ink inside a flow path, and is performed in a preliminary discharge position different from a printing position inside an inkjet recording apparatus, the printing position being in which ink is printed on a print medium.
According to a configuration discussed in Japanese Patent Application Laid-Open No. 2005-28741, printing discharge using a large discharge port can refresh ink. However, when a small discharge port and a large discharge port are simultaneously used for printing discharge, or a small discharge port is used immediately after a large discharge port is used for printing discharge, there are cases where an ink full state of the small discharge port is disturbed. Since the small discharge port and the large discharge port are provided adjacent to each other, such cases occur due to influences of ink flow and pressure wave caused by discharge of liquid droplets from the large discharge port and refill of liquid droplets. Consequently, normal discharge is unlikely to be performed from the small discharge port.
When a small discharge port and a large discharge port are simultaneously used for preliminary discharge, or a small discharge port is used immediately after a large discharge port is used for preliminary discharge, an ink full state of the small discharge port is disturbed by similar reasons as the printing discharge. Consequently, normal preliminary discharge is unlikely to be performed from the small discharge port. Thus, the preliminary discharge using the small discharge port and the large discharge port needs to be temporally separated. Although the preliminary discharge is performed in a preliminary discharge position, a printing operation cannot be performed during the preliminary discharge, thereby causing a reduction of printing speed.